Android : DRM on Chromecast Custom Receiver [on hold]

I have implemented a media player than can cast mp4 videos using this sample provided by Google.

https://github.com/googlecast/cast-custom-receiver/blob/master/sample_media_receiver.html][1]

I am wondering how I can add DRM functionality to this? What do I need to do in the receiver end and in the sender end to add DRM support? How do I specify lincense info, etc? The sender is an android application.

I am not sure where to start for DRM. Any tutorials on how to do this?